1. Field of the Invention
The present invention is generally directed toward heating, ventilation, and air conditioning control systems and, more specifically, toward such control systems used in automobiles.
2. Description of Related Art
Automobile heating, ventilation, and air conditioning systems (hereafter HVAC systems) have conventionally included controls and vents located in or around the dashboard. However, as is well known to anyone who has been in a car having a conventional HVAC system, there is a significant difference in temperature between the front portion and the rear portion of the passenger compartment, especially on days with extreme conditions (hot, sunny days and cold days). Providing all of the vents at the front of the vehicle usually maintains uncomfortable temperature conditions for passengers in the rear portion of the vehicle. Alternatively, if an effort is made to make the rear passengers comfortable, the front passengers are over-heated or over-cooled.
Accordingly, HVAC controls and vents in a rear portion of the passenger compartment, which are in addition to the conventional HVAC controls and vents provided at the front portion of the passenger compartment, have been developed. Such a conventional automobile HVAC control system 10 including parallel front and rear HVAC control systems 12, 14, respectively, is illustrated in FIG. 1. The front HVAC control system 12 controls operation of a front HVAC system, which includes a heater core, a compressor, an evaporator, dampers, and a blower fan. The rear HVAC control system 14 controls operation of a rear HVAC system, which includes a heater core, an evaporator, dampers, and a blower fan. The front and rear heater cores are on the same fluid circuit. A compressor supplies refrigerant to both the front and rear evaporators.
The front HVAC control system 12 includes a multi-function front control panel 16, a damper, air conditioning, and blower control panel 18, a microprocessor 20, a plurality of actuators 22, 24, 26, sensors 28, a power transistor 30, and a blower 32, which is driven by the power transistor 30. The actuators include a recirculation/fresh air (R/F) actuator 22, a mode actuator 24, and an air mix actuator 26. The front panel 16 includes an automatic control setting button 34, recirculation/fresh air button 36, temperature set-point adjustment buttons 38, an off button 40, a front defrost button, a rear defrost button, and a display 42. The damper, air conditioning, and blower control panel 18 includes air flow direction buttons 44, blower speed control buttons 46, and air conditioning on/off buttons 48.
User-input operational parameters and sensed conditions are transmitted to the microprocessor 20. The microprocessor 20 controls the actuators 22, 24, 26 and power transistor 30 in accordance with the user inputs made via the front control panel 16 and the damper, compressor, and blower control switch panel 18 and, if in automatic mode, in accordance with a predefined control algorithm in response to sensed conditions. The sensed conditions include interior/exterior temperature, solar radiation, evaporator temperature, water temperature, and switch panel settings.
The rear HVAC control system 14 includes a rear manual switch 50 and a rear control panel 52. The rear manual switch 50 is disposed adjacent the front control panel 18 and alternatively enables or disables manual control over the rear HVAC system, thereby activating/deactivating the rear HVAC control system 14. The rear manual switch 50 is movable between a plurality of positions, including an off position, a rear manual control enabled position, vent/cold blower speed control positions, and heat/hot blower speed control positions.
Placing the rear manual switch 50 in the off position disables the rear HVAC system. Placing the rear manual switch 50 in the rear manual control enabled position permits manual control of the rear HVAC system via the rear control panel 52. Placing the rear manual switch 50 in any of the rear vent/cold and heat/hot blower speed control positions directly controls the rear HVAC system (mode and blower speed). Whether rear air conditioning is active (as opposed to vent) depends upon the condition of the auto button 34 on control panel 16 or the air conditioning buttons 48 on the damper, air conditioning, and blower speed control panel 18.
The rear control panel 52 includes a mode selector switch 54 and a blower speed selector switch 56. A mode actuator 60 receives signals from the mode selector switch 54 or the rear manual switch 50 to operate the rear HVAC system in the user-selected mode (vent/heat) and blower relays 62 are actuated by the blower speed selector switch 56 or the rear manual switch 50 to operate a blower 64 at the desired speed.
In the conventional HVAC control system, the rear HVAC system is either manually operable by the rear manual switch 50 or manually operable by the control panel 52, at the discretion of the front passengers. In this arrangement, the front and rear HVAC control systems 12, 14 are truly parallel, with no communication of operating instructions between the front and rear HVAC control systems 12, 14.
The foregoing conventional HVAC control system 10 suffers from a number of disadvantages. Since the front and rear control systems 12, 14 are in parallel, and there is no communication between the front and rear HVAC control systems 12, 14. Also, modern front HVAC control systems 12, such as the one illustrated in FIG. 1, have the automatic control setting wherein compressor activation (A/C), air mix (temperature), mode of operation (vent/heat), recirculation/fresh air, and blower speed are controlled such that cabin temperature matches or tracks a user-defined temperature set point in response to sensed conditions (i.e., interior/exterior temperature, solar radiation, etc.). The automatic control setting operates under a control algorithm based upon predefined experimental models, and is typically tuned or customized to match the physical characteristics (i.e., cabin size, glass area, insulation properties) of the subject automobile. Since the conventional rear HVAC control system 14 is not in communication with the front HVAC control system 12, automatic operation or control of the rear HVAC system is not possible with the conventional control arrangement.
Therefore, there exists a need in the art for an automobile HVAC control system that provides the front passengers with improved control over the rear HVAC system. There also exists a need in the art for a rear HVAC control system that is operable in an automatic mode in response to sensed environmental conditions. Finally, there exists a need in the art for front and rear HVAC control systems that permit better control over cabin temperature while permitting front and rear passengers to manually control the HVAC system to satisfy individual temperature requirements.